The project continues our investigations into the effects of bile acids and fatty acids on intestinal water and solute transport. In the coming year we plan to investigate further the mechanisms of the pH dependence of intestinal fluid secretion induced by detergent compounds. To this end, we will study the effects of nonionic detergent, monoolein, at pH 4.0 and pH 7.6 in the human jejunum. To test the hypothesis that effects of biological detergents on intestinal water transport can be explained as the result of a combination of fluid secretion induced by cyclic AMP-mediated process and enhanced intestinal permeability, we plan to study the combined effects of cholera toxin-induced fluid secretion and enhancement of intestinal permeability by the administration of amphotericin B in the rat small intestine and colon. To test the hypothesis that bile acids interact with intestinal mucosa as monomers and that the protective effect observed by the presence of lecithin is the result of a reduction of monomer concentration of bile acids, we plan to develop an in vitro system which allows to measure monomer concentration of bile acids.